Flash-producing apparatus



Feb. 15, 1944. H. E. GRIER FLASH PRODUCING APPARATUS Original Filed Jan. 51, 1939 Patented Feb. 15, 1944 UNITED. STATES PATENT OFFICE FLASH-PRODUCING APPARATUS Herbert Earle Grier, Newton Center, Mass.

Original application January 31, 1939, Serial No. 253,760. Divided and this application August 4, 1940, Serial No. 351,426

9 Claims.

The present invention relates to electric systems, and more particularly to condenser-charging-and-discharging systems.

A system in common use for flash-producing and similar purposes comprises a condenser charged from a source of direct current, the charge of which is thereupon dissipated in a discharge circuit comprising a gaseous-discharge device, like a flash-lamp. The resulting flash may, for example, be used in flash-photography.

It is very important, in order to obtain proper flashing or other operation, that the condenser be charged at the proper rate. If the condenser be charged at too rapid a rate, for example, the flash-tube will not deionize after it has operated.

Instead of rapid flashes, with prompt extinguishment after each flash, the result will be a continuous glow through the tube. If the charging rate is too slow, on the other hand, the condenser will not become fully charged before each flash, thus resulting in impaired intensity of the flashes.

A condenser-charging resistor or other impedance has heretofore been inserted between the condenser and its charging source, in order to provide for a proper charging rate of the condenser. The size and characteristics of this resistor or other impedance have been determined by the characteristics of the flash-tube or other apparatus and the desired time interval between the condenser discharges.

The use of the additional condenser-charging impedance is attended with disadvantages, among them the disadvantage that it is necessary to provide means for dissipating the heat losses introduced by the resistance of this impedance.

An object of the invention is to improve the efficiency of condenser-charging systems of the above-described character.

' 'Another object of the invention is to provide a new and improved condenser-charging circuit of the above-described character that shall not require the use of the said additiona1 resistor or other charging impedance.

The source of direct current heretofore employed for charging the condenser has usually been either a battery or an alternating-current source, the latter having a supply transformer the primary winding of which is connected to the alternating-current source and a rectifier for rectifying the current supplied by the secondary winding. 1

The present invention is more particularly related to condenser-charging circuits the energy sources, and a further object oi the invention is to replace the before-described condensercharging resistor or other impedance by a. special secondary winding for the supply transformer that shall perform the function not only of the secondary winding, but also of the charging impedance. Incidentally, this special secondary winding will operate also to prevent damage to the rectifier.

Other and further objects will be described hereinafter and will be particularly pointed out in the appended claims.

The invention will now be described more fully in connection with the accompanying drawing, the single figure of which represents a circuit diagram embodying the invention.

The flash-lamp 18 may be of any desired type. It is illustrated as of the type more fully described in Letters Patent 2,277,697, granted March 31, 1942, upon application Serial No. 253,760, filed January 31, 1939, of which the present application is a division. The flash-lamp i8 is shown as U -shaped, and mounted in an elongated glass-bulb jacket or envelope 92, cemented at 24 to a flat, insulating base 94 provided with five pin terminals 6, I0, l2, I4 and 18 projecting exteriorly thereof. A continuous light source, such as an incandescent lamp I6, is shown mounted between th arms of the U of the U- shaped flash-lamp Hi. The flash-lamp I8 is provided with two terminals, constituted of a cathode l and an anode 9, connected, respectively, to the terminals 6 and I2. The parts are held permanently steady in correct position, and properly lined up, in the bulb 92 by means of suitable metal spreaders 20. One end of a high-voltage spark trigger or trip wire electrode 22 is provided with a terminal ll that is connected to the terminal l4, and its other end is free, as shown. The lamp [6 is provided with terminals'that are respectively connected to the terminals 18 and I The apparatus may be used in conjunction with a control circuit 11, such as shown. The flashlamp I8 is shown connected, through the medL- um of the terminal pins 12 and 6, across a condenser'll. To this end, the terminal pin I2 is connected to a terminal l5 at one side of the condenser II by conductors 3| and Z1; and the terminal pin 6 is connected to the other side of the condenser II by a conductor 29. The condenser ll may be subjected to a voltage of, say, 2000 volts from any direct-current supply. The preferred supply is shown as a transformer 26, the primary winding 28 of which may be connected of which is supplied by alternating-current 53 to any desired source of alternating energy of the correct voltage and frequency, and the secondary winding 88 of which may be connected to the condenser II through a rectifier 12. The secondary winding 38 may have a high impedance for performing the normal current-limiting function of a charging impedance, thus eliminating the necessity for the use of a separate charging resistor or other impedance between the secondary winding 38 and the charging condenser II. The proper charging rate of the condenser II, and consequent proper flashing of the tube I8, is thus obtained, notwithstanding the absence of the separate condenser-charging resistor or other impedance heretofore employed. The secondary winding 38 may be designed with due regard to the characteristics of the tube I 8 and the interval of time desired between flashes thereof. The secondary winding 30 should be so designed that the short-circuit current shall be limited not to exceed the peak rating of the associated rectifier tube 12.

For simplicity, the connections to a source of power for the lamp I6, through the medium of the terminals I8 and 18, are not shown. The lamp I6 is generally connected in parallel with the primary winding 28 of the transformer 28.

Atrigger tube I may be connected to terminals I and I3, across a bleeder resistor 8|, so as to be supplied with voltage therefrom. The bleeder resistor BI is connected, in series with a bleeder resistor 82, across the condenser I I, which constitutes the main powersupply for the tube I. Power for the tube I may, however, be obtained, if desired, from a separate power-supply. The resistors 8| and 82 are so proportioned that a desired voltage of, say, 300 volts shall appear across the terminals I3 and I5 of the resistor 8|. To the terminals I3 and I5 there are also connected, in parallel with the tube I, in series with a condenser 40, a primary winding 14 of a transformer 36. One side of the condenser 40 is connected to the terminal I3 and the other side, by way of a conductor 90, to the primary winding 14. The secondary winding 38 of the transformer 36 is connected, by a conductor 31, to the terminal I1 of the trip wire 22, to produce the high-voltage triggering spark. Itwill be observed that the terminal I1 of the trip wire 22 is alone connected to the secondary winding 38. The return path is by capacity coupling of the wire 22 to the electrode of the lamp I8.

The tube I may be of the cold-cathode gaseous-discharge type illustrated and described in Letters Patent 2,185,189, 2,201,166 and 2,201,167 issued to Kenneth J. Germeshausen on January 2, 1940, and May 21, 1940. It may comprise an evacuated glass envelope I filled with a suitable gas, such as neon, or any of the other noble gases, such as argon or helium. The tube contains several electrodes, namely, a solid cathode 2, an anode Or plate 5, and one or more grids, inner and outer grids being shown at 3 and 4, between the anode 5 and the cathode 2. Either grid may be used as the control grid, depending flash-tube, a trigger thyratron, and a condenser for discharging through the thyratron, the condenser being charged from a bleeder resistor. The control electrode of the thyratron is connected, through a resistor, to the negative end of the source of energy for energizing the bleeder resistor, in order to impress a negative bias on the control electrode of the thyratron. According to the present arrangement, however, the resistors 95 and 99 are connected directly to the cathode 2. As explained in the said Germeshausen Letters Patent, the cathode 2 may comprise a material that will break down under the action of a cathode spot to form on the cathode a surface coating of a material of relatively low work-function.

This cathode spot is more easily formed on a pill of caesium chloride and aluminum filings or powder than on pure caesium.

As explained in the said Letters Patent 2,185,189, the grid 3 may, in normal use, be positioned close to the cathode 2, say, not more than a few millimeters from the cathode, and may be of such shape that the cathode will sputter a coating of a material of low work-function, such as caesium, onrthe grid surface during the normal operation of the tube.

The flash-lamp I8 may be tripped by means of a hand-controlled switch (not shown) or, as illustrated, by an automatically operated contactor that is shown connected across the anode or plate 5 and the grid 4 of the tube I. The contactor 85 may be actuated by the object being photographed, or by the camera shutter. The connections may be traced from the grid 4, through a blocking condenser 96 and a leak resistor 81, in parallel, by way of a conductor 8|, through the contactor 85, and by way of a conductor 93 and the conductor 21, to the anode I. The trigger tube I is thus, through the contactor 85, connected to its grid 4, caused to flash the flash-lamp I8 at the desired instant. The grid 4 may also be actuated by a photo-electric cell or by a microphone through a suitable amplifier.

In the operation of the circuit, the condenser I I starts to become charged from the direct-current source 25, 12, the tube I being non-conductive. The source charges the condenser 40, at the same time, through the resistor 8| and the primary winding 14. At any time after the voltage across the condenser II reaches its maximum value, the contactor 85 may be caused to function, raising the potential of the grid 4 until the breakdown voltage between the grid 4 and the cathode 2 or the grid 4 and the grid 3 is exceeded, and the trigger tube I becomes conducting. The condenser 40 then discharges through the condenser-discharge circuit comprising'the tube I and the primary winding 14 of the transformer 88. The resulting voltage surge of the secondary winding 38 of the transformer 36 is applied to the triggenelectrode 22 of tube I8. This causes the gas in the tube I8 to .ionize, permitting the condenser U to discharge through the flash-lamp I8 between its electrodes, producing a very brilliant flash of short duration. When the con.- denser ll "is fully discharged, the tube extinguishes and the cycle is ready for repetition. It will be noted that when the condenser II is fully discharged, the voltage across the resistor 8| is zero, preventing the condenser 40 from charging again and allowing the tube to deionize. The time taken for the circuit to function from the closing of the contactor 85 to the flash of light from the tube I8 is very brief.

With the aid of this invention, it is possible to produce a brief flash of light at any desired instant for taking photographs.

Modifications will occur to persons skilled in the art and all such are considered to fall within the scope and spirit or the invention.

What is claimed is: 1. An electric system comprising a gaseousdischarge device, a supply transformer having a transformer winding, a condenser, a rectifier,

means for connecting the condenser to the trans- 1 former winding through the rectifier to cause the condenser to become charged from the transformer, the transformer winding having a high impedance in order to limit the short-circuit current to below the peak rating of the rectifier, whereby the condenser may be connected to the transformer winding through the rectifier withv having a high impedance in order to limit the short-circuit current to below the peak rating of the rectifier, whereby the condenser may be connected to the secondary winding through the rectifier without the interposition of an additional condenser-charging impedancemeans for connecting the Condenser to the flash-lamp, and means for causing the condenser, after it has become charged, to discharge through the flashlamp.

3. Flash-producing apparatus comprising a flash-lamp, a supply transformer having a primary winding and a secondary winding, a condenser, a rectifier, means for connecting the condenser to the secondary winding through the rectifier to cause the condenser to become charged from the transformer, the secondary winding having a high impedance in order to limit the short-circuit current to below the peak rating of the rectifier, whereby the condenser may be connected to the secondary winding through the rectifier without the interposition of an additional condenser-charging impedance, a trigger device, means for connecting the condenser to the flashlamp, and means for causing the condenser, after it has become charged, to discharge through the flash-lamp under the control of the trigger device.

4. Flash-producing apparatus comprising a flash-lamp; a supply transformer having a primary winding and a secondary winding, a condenser, a rectifier, means for connecting the condenser to the secondary winding through the rectifier to cause ,the condenser to become charged from the transformer, the secondary winding having a high impedance in order to limit the short-circuit current to below the peak rating of the rectifier, whereby the condenser may be connected to the secondary winding through the rectifier without the interposition of an additional condenser-charging impedance, a trigger device, a bleeder resistor connected to the secondary winding to constitute the bleeder resistor a source of energy, means for connecting the trigger device to the bleeder resistor in order that the trigger device may become energized from the bleeder resistor, the trigger device being normally inefiective when energized, means for rendering the trigger device efi'ective, means for connecting the condenser to the flash-lamp, and means for caus- 5 ing the condenser, after it has become charged, to discharge through the flash-lamp when the trigger device becomes efiective.

5. Flash-producing apparatus comprising a flash-lamp, a supply transformer having a pri- 0 mary winding and a secondary winding, a condenser, a rectifier, means for connecting the condenser to the secondary winding through the rectifier to cause the condenser to become charged from the transformer, the secondary winding having a high impedance in order to limit the short-circuit current to below the peak rating of the rectifier, whereby the condenser may be connected to the secondary winding through the rectifier without the interposition of an additional condenser-charging impedance, a second condenser, means for charging the second condenser, means for discharging the second condenser after it has become charged, means for connecting'the first-named condenser to the flash-lamp, and means for causing the first-named condenser, after it has become charged, to discharge through the flash-lamp when the second condenser is discharged.

6. Flash-producing apparatus comprising a flash-lamp, a supply transformer having a primary winding and a secondary winding, a condenser, a rectifier, means for connecting the condenser to the secondary winding through the rectifier to cause the condenser to become charged from the transformer, the secondary winding having a high impedance in order to limit the short-circuit current to below the peak rating of the rectifier, a gaseous-discharge trigger device comprising an anode, a cathode and a control electrode, a second condenser, a bleeder resistor and a second resistor connected in series to the secondary winding to constitute the bleeder resistor a source of energy, means for charging the second condenser from the bleeder resistor, means for connecting the second condenser to the anode and the cathode to energize the trigger device from the bleeder resistor, means for controlling the control electrode to cause the second condenser to discharge through the trigger device, means for connecting the first-named condenser to the flash-lamp, and means for causing the first-named condenser, after it has become charged, to discharge through the flash-lamp when the second condenser discharges through the trigger device.

7. Flash-producing apparatus comprising a flash-lamp, a condenser, means for charging the condenser, a gaseous-discharge trigger device comprising an anode, a cathode and a control electrode, a resistor, means for connecting the cathode and the control electrode through the re- ,sistor, a second condenser, a. bleeder resistor, means for energizing the bleeder resistor so that it may constitute a source of energy, means ,for charging the second condenser from the bleeder resistor, means for connecting the second condenser to the anode and the cathode to energize the trigger device from the bleeder resistor, means 7 for controlling the control electrode to cause the second condenser to discharge through the trigger device, means for connecting the first-namedcondenser to the flash-lamp, and means for causing the first-named condenser, after it has become charged, to discharge through the flash- Q lamp when the second condenser discharges through the trigger device.

8. An eiectric system comprising a gaseousdischarge device, a supply transformer having a transformer winding, a condenser, a rectifier, means for connecting the condenser to the transformer winding through the rectifier to cause the condenser to become charged from the trans former, the transformer winding having a high impedance, whereby the condenser may be connected to the transformer winding through the rectifier without the interposition of an additional condenser-charging impedance, means for connecting the condenser to the gaseous-discharge device, and means for causing the condenser, after it has become charged, to discharge through the gaseous-discharge device.

9. Flash-producing apparatus comprising a flash-lamp, a supply transformer having a primary winding and a secondary winding, 2. condenser, a rectifier, means for connecting the condenser to the secondary winding through the rectifier to cause the condenser to become charged from the transformer, the secondary winding having a high impedance, whereby the condenser may be connected to the secondary winding through the rectifier without the interposition of an additional condenser-charging impedance, means for connecting the condenser to the flashlamp, and means for causing the condenser, after it has become charged, to discharge through the flash-lamp.

HERBERT E. GRIER. 

